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<table width="100%" summary="page for mackp"><tr><td>mackp</td><td style="text-align: right;">R Documentation</td></tr></table>

<h2>Prediction grid data for 1992 mackerel egg model</h2>

<h3>Description</h3>

<p> This data frame provides a regular grid of values of some predictor variables useful for modelling mackerel egg abundances. Its main purpose is to enable mackerel egg densities to be predicted over a regular spatial grid within the area covered by the 1992 mackerel egg survey (see <code>mack</code>), using a fitted generalised additive model.
</p>


<h3>Usage</h3>

<pre>
data(mackp)
</pre>


<h3>Format</h3>

<p>A data frame with 5 columns. Each row corresponds to one spatial location within the survey area. 
The columns are as follows:
</p>

<dl>
<dt>lon</dt><dd><p>Longitude of the gridpoint in degrees east</p>
</dd>
<dt>lat</dt><dd><p>Latitude of the gridpoint in degrees north.</p>
</dd>
<dt>b.depth</dt><dd><p>The sea bed depth at the gridpoint.</p>
</dd>
<dt>c.dist</dt><dd><p>The distance from the gridpoint to the 200m sea bed depth contour.</p>
</dd>
<dt>salinity</dt><dd><p>Salinity interpolated onto the grid (from <code>mack</code> measurements).</p>
</dd>
<dt>temp.surf</dt><dd><p>Surface temperature interpolated onto grid (from <code>mack</code> data).</p>
</dd>
<dt>temp.20m</dt><dd><p>Temperature at 20m interpolated from <code>mack</code> data.</p>
</dd>
<dt>area.index</dt><dd><p> An indexing vector that enables straightforward copying of
the other variables into a matrix suitable for plotting against longitude and
lattitude using <code>image()</code>. See the example below.</p>
</dd>
</dl>


<h3>Details</h3>

<p> The grid is defined on a series of 1/4 degree lon-lat squares.
</p>


<h3>References</h3>

<p>Borchers, D.L., S.T. Buckland, I.G. Priede and S. Ahmadi (1997) &quot;Improving the precision of the daily egg 
production method using generalized additive models&quot;. Can. J. Fish. Aquat. Sci. 54:2727-2742. 
</p>


<h3>Examples</h3>

<pre>
## example of how to use `area.index' to paste gridded info.
## into a square grid (of NA's) for plotting
data(mackp)
lon&lt;-seq(-15,-1,1/4);lat&lt;-seq(44,58,1/4)
zz&lt;-array(NA,57*57)
zz[mackp$area.index]&lt;-mackp$b.depth
image(lon,lat,matrix(zz,57,57))
</pre>


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